A conventional type of alkaline cell employs a cathode comprising predominantly an oxidic depolarizer such as manganese dioxide usually admixed with a binder and conductive material such as graphite, steel wool and the like. The anode usually comprises a consumable anodic material such as powder zinc admixed with a gelling agent such as carboxymethyl cellulose, a suitable alkaline electrolyte such as an aqueous potassium hydroxide solution, and if desired, mercury. The gel anode is then extruded to form a desired shaped electrode. Anode materials and their preparation are described in U.S. Pat. Nos. 2,938,064 and 2,935,547 issued to K. Kordesch and U.S. Pat. No. 2,993,947 issued to E. E. Leger. The above electrodes together with conventional separator material can be assembled into an alkaline-MnO.sub.2 /zinc cell.
Discharging the above described cell on a microampere drain or on very intermittent discharge has resulted in zinc oxide formation in the separator which can result in internal shorts. Specifically, zinc oxide in contact with metallic zinc is known to be conductive and thus an internal electronic path is formed between the anode and cathode. An investigation of the internal shorting problem has revealed the carboxymethyl cellulose to be a major contributor to the transporting and precipitating of the zinc oxide throughout the cell. This internal shorting causes wasteful consumption of the components of the cell resulting in lower output capacity.
It is an object of the present invention to provide an alkaline-MnO.sub.2 cell that can be discharged on microampere drains without internally shorting.
It is another object of the present invention to provide a powder-gel anode for alkaline-MnO.sub.2 cells that employs P-N-V-P and/or PMA with or without carboxymethyl cellulose as the gelling agent.
It is another object of the present invention to provide a powder-gel anode comprising powder zinc, poly-N-vinyl pyrrolidone and/or polymethacrylic acid with or without carboxymethyl cellulose and an aqueous alkaline electrolyte.
It is another object of the present invention to employ poly-N-vinyl pyrrolidone and/or polymethacrylic acid as a gelling agent and lubricating agent for powder-gel anodes.
The foregoing and additional objects will become more fully apparent from the following description.